Training Considerations

Control System Design Concepts
Design Approaches
Governor Controls
Redundancy
Implementation Strategies
Security Issues
Training Considerations

What Is Small?
• The definition of a small hydro project varies
• Generating Capacity
• Micro 0 – 100 kW
• Mini 100 – 1000 kW
• Small 1000 – 10,000 kW

Control System Design Concepts
• Legacy Hardwired Systems
• Remove Legacy Hardwired Control System and
Replace with a new PLC/HMI Based Control System
• Hybrid (combination of Legacy Hardwired and
PLC/HMI based systems)
• Remote Terminal Units (RTUs)
• Which is Best for Small Hydro?

Legacy Hardwire Systems

Legacy Hardwired System
• Advantages
• Already in service
• No upfront capital costs
• Disadvantages
• Higher long-term operating and maintenance costs
• Little operations/maintenance data
• Harder to troubleshooting
• More equipment to calibrate and maintain
• Modern Operations
• Lower efficiencies
• Lower reactivity to system upsets
• Harder to operate/monitor remotely

Remove Legacy System
Install PLC/HMI Based System

Remove Legacy System
Install PLC Based System
• Advantages
• Less expensive to implement than Hybrid Systems
• Less field work
• Engineering is more straightforward
• Less construction activities
• Lower long-term operating and maintenance costs
• Significant additional operations/maintenance data
• Simplified troubleshooting and calibration activities
• Modern operations
• Additional efficiency
• Significantly increases remote operation/monitoring

Remove Legacy System
Install PLC Based System
• Disadvantage
• The biggest disadvantage is the loss of a hardwired
“back-up” control system. If the PLC/HMI system
malfunctions then the unit(s) is shutdown until the
control system is repaired.
• The loss of the “back-up” control system can be
somewhat mitigated with redundancy design in the
PLC/HMI system. However, this will increase cost and
off-set any savings gained from not implementing a
Hybrid system.

Maintain Legacy System
Install PLC/HMI Based System (Hybrid)

Hybrid System
• Advantages
• The biggest advantage with integrating the PLC/HMI based
system with the Legacy system is the redundancy. If one
system is down, the other will still function
• Improved long-term operating and maintenance costs of
Legacy systems
• Significant additional operations/maintenance data
• Simplified troubleshooting and calibration activities
• Modern operations
• Additional efficiency
• Significantly increases remote operation/monitoring

Hybrid System
• Disadvantages
• Most expensive to implement
• Significant field work
• Engineering is more complicated
• Increased construction activities
• Requires legacy equipment to be calibrated and
maintained

Remote Terminal Unit (RTU)

RTU
• Advantages
• Low initial cost
• Remote monitoring and control (limited)
• Disadvantages
• Higher long-term operating and maintenance costs
• Same as Legacy System, plus new RTU
• Modern Operations
• Same as Legacy System, except for limited remote monitoring
and control.

Control System Design Concepts
SYSTEM
INITIAL COST
OPERATING &
MAINTENANCE COST
UNIT & PLANT
CONTROLLABILITY
Legacy Hardwired N/A High Low
PLC & HMI (only) Medium Low Medium
Hybrid System High Medium High
RTU Low High Low
Small Hydro with Legacy Hardwired systems often benefit most from the
RTU option due to the low initial cost and minimal gains in O&M and
controllability.
New Small Hydro systems often benefit most from the PLC & HMI (only)
option due to the savings from hardwired controls (distributed I/O) and
gains in O&M and controllability.

Design Approaches
• Distributive: PLC I/O throughout facility with
distributed racks networked to the processor
• Centralized: PLC I/O hardwired to on common place
where the PLC I/O racks and the processor are
located

Distributive Design
FACILITY
CONTROL ROOM
HARDWIRE
NETWORK
PLC PROCESSOR RACK
PLC REMOTE RACK
PLC REMOTE RACK
PLC REMOTE RACK

Centralized Design
FACILITY
CONTROL ROOM
PLC PROCESSOR RACK
HARDWIRE
NETWORK
PLC REMOTE RACK
PLC REMOTE RACK
PLC REMOTE RACK

Design Approaches
SYSTEM INSTALLATION COST SECURITY MAINTENANCE TROUBLESHOOTING
Distributive Medium Low
Harder (Distributed over
large area)
Easier (connection are local to
devices)
Centralized High High
Easier (Local connections
and controls equipment)
Harder (connections are not local to
devices)

Governor Controls
• Fly Ball
• Digital Governor
• Gate Positioner (PLC)

Governor Controls
SYSTEM INSTALLATION COST RESPONSE TIME ISOCHRONOUS CONTROL
Fly Ball N/A Medium Medium
Digital Governor High High High
Gate Positioner Medium Medium Medium
Small Hydro with Legacy Fly Ball governors often benefit from a retrofit to a
Gate Positioner. New Small Hydro often benefits from a Gate Positioner, unless
Isochronous Control is very important and dynamic in which a Digital Governor
should be used.

Redundancy
• Power Supply Redundancy
• PLC Redundancy (option A): Redundant I/O cards (in a
single rack), processors (in a single rack), and power
supplies.
• PLC Redundancy (option B): Redundant I/O racks, processor
racks, and power supplies.
• PLC Redundancy (option C): Redundant I/O racks,
processor racks, networking equipment, networking cables,
and power supplies.
• Full Redundancy
• Small Hydro often benefits most from Power Supply
Redundancy only.

Security Issues
• Physical Security
• Physical security of a previously occupied station (e.g., remote cameras,
access controls)
• Locked six-walled enclosure for networking equipment, with access
controls
• Cyber Security
• Use of firewalls, threat managers, etc.
• Choice of network protocols
• Choice of media
• Hardening of PCs, servers, switches, routers, etc.
• NERC-CIP provides rules, regulations, and guidance
• Small Hydro can often be classified as non-critical assets and can
there keep the security requirements low. If the station is classified
as a black start asset and used for bootstrapping the grid, however, it
may be classified higher requirements more strict security.

Training Considerations
• Modern automation system are fundamentally different
from legacy hardwired systems and require a different set
of skills to maintain
• Computer savvy
• Program applications knowledge
• Networking knowledge
• Understanding of I/O hardware and configurations

Training Considerations
• Operating modern automations, via and HMI, is also
fundamentally different and requires additional training
• Computer savvy
• HMI menus, paging, and graphics
• Trending capabilities and configurations
• Alarm classes and alarm management
• How legacy systems and automation systems
interact (in hybrid systems)

Summary
• Each stakeholder—owners, engineers,
operators, and maintenance staff—should be
fully engaged during all stages of the design,
construction, and start-up process of a hydro
unit or hydro station automation upgrade.
• Discussion between all stakeholders should
included Design Concepts, Design Approaches,
Implementation Strategies, Security Issues,
and Training Considerations